Expensive time consuming process In this case, the regulators in each drop line must be backed off to zero pressure, otherwise some drop lines will randomly have no flow or not enough flow. Given the lack of balance between drop lines in this condition, the shut-off valves on all drop lines except one must be closed. Then, one valve for one drop line antique oil paintings for sale must be opened at a time in order to ensure that each drop line is cleaned. Cleaning can involve generally four or five progressive cleaning steps and a typical circulation system can easily have 30 drop lines, making the cleaning process a large and expensive task. When the new paint is introduced at a different abstract oil paintings for sale viscosity it can take up to five days to balance these systems with two trained operators. To do this effectively a flow meter must be inserted sequentially in each drop line and the pressure regulator/pressure reducing valve in the drop line must be adjusted until the correct flow is obtained. Each time the next drop line is adjusted it affects the flow Oil Paintings for sale rate through the previously adjusted drops. Thus, many iterations are required until all drops are within an acceptable range. This is an expensive time consuming process. Related articles: 1 The spray painting of automobile bodies